: So I doubt it's a slip-up and they meant 2558 not 2560.

: Chances are, they're going with a later date because we don't know how much
: time the Halo 5 campaign is going to span. For all we know, we start in
: late 2558 and the game ends in 2560 with the Chief dying.

: Then Locke appears as the main character for Halo 6, until a big reveal later
: that Chief is alive(probably because of the Librarian's
: "Enhancing" his evolution.)

: Just a guess. :3
If this is referring to events in Halo 5, and not afterward, this might just be the UNSC announcing it some time after it occurred. The "death" of The Chief would be something to give ONI's PR people pause.

It also seems like a prologue to the All Hail ad, where Locke finds Chief in a state of distress after a Guardian attack.